Alternate mental subtraction method

[Shalek]

I've used a similar technique, this is such an improvement though.

[ReasonGuysCopyright]

9456-7589

7589=7590-1__(1)

7590=7600-10__(11)

7600=8000-400__(411)

8000=9000-1000__(1411)

9456=9000+456__(1867)

I do it slightly differently in my head, but I always found this technique of pulling the numbers together as easier that pushing them down.

[spelldragon93]

Lol, I already do this in my head and it really does work! The only thing is I make it faster (and riskier) by keeping in mind the original number instead of memorizing new sets again and again. I mean to say that it is an identical process, except I take the emphasis off of reinforcing constantly new sets of numbers as they come and instead keep in mind three number (the changing one, the original one, and what I'm subtracting) and use the original number to guesstimate if I'm doing it right.

[WiFi8679]

This Method also Works Gr8t WIth three digit numbers too

Many Thanks Khan academy

[AlmostAmerican]

I've never seen that method before of doing all the borrowing at once! Very interesting!

[coolflyingpenguin]

I like to do it like this:

1 + 7589 = 7590

10 + 7590 = 7600

400 + 7600 = 8000

1456 + 8000 = 9456

1 + 10 + 400 + 1456 = 1867

[teawead]

@coolflyingpenguin

Your technique works efficiently with whole numbers. I will remember this!